Polypropylene Laminate Wallcovering

ABSTRACT

The present invention provides a wallcovering comprising a laminate of three layers including: (1) a scrim backing layer, (2) a specially formulated, oriented polypropylene (OPP) film forming a substrate layer that is printable, and (3) a UV Cured Clear Coating or an oriented polypropylene film as a top layer forming a top layer.

FIELD OF THE INVENTION

The present invention relates to wallcoverings. More particularly, thepresent invention relates to a polypropylene laminate wallcovering.

BACKGROUND OF THE INVENTION

Polyvinyl chloride (PVC) is a standard material for producing commercialwallcoverings. PVC wallcoverings are relatively low cost, have highdurability properties relative to weight, have good printing propertiesand embossing properties, and are flexible from an installationperspective. PVC wallcoverings, however, have drawbacks. The mostserious drawback is the environmental hazard that polyvinyl chlorideposes. PVC wallcoverings produce environmental hazards during themanufacturing stage, when the finished PVC wallcovering is installed,and when the PVC wallcoverings are eventually discarded.

Alternatives to PVC wallcoverings have failed in one or all of thefollowing categories: Too expensive, poor print registration, poor graincapture (does not emboss well), does not meet Type II wallcoveringprotocol, which includes the ASTM E-84 Class A flammabilityrequirements, and many other performance criteria as stated in CCC-W-408A and CCC-W-408-D.

A need therefore exists for an improved, environmentally friendlywallcovering that is low cost, has good printing and embossingcharacteristics, and meets standard performance criteria, includingflammability requirements.

SUMMARY OF THE INVENTION

The present invention answers this need by providing a wallcoveringcomprising a laminate of three layers including: (1) a scrim backinglayer, (2) a specially formulated, oriented polypropylene (OPP) filmforming a substrate layer that is printable, and (3) a top layercomprising either a clear, ultraviolet (UV) cured coating (an over printvarnish (OPV)) or an oriented polypropylene film. The orientedpolypropylene film used for the substrate layer has good printregistration and excellent grain capture when embossed and is comparablein cost, if not less expensive, than standard Type II PVC film. Theoriented polypropylene film used as a substrate in the laminatewallcovering of the present invention has been specially engineered toaccept printing inks and adhesives for laminating purposes.

It is thus an object of the present invention to provide a polypropylenelaminate wallcovering that has the look, feel, and performancecharacteristics of conventional PVC wallcoverings without theenvironmental drawbacks associated with PVC wallcoverings. Thewallcovering, constructed in accordance with the present invention, alsohas a Class A flame rating.

Further objects, features and advantages will become apparent uponconsideration of the following detailed description of the inventionwhen taken in conjunction with the drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-section view of the wallcovering in accordance withthe present invention.

FIG. 2 is an exploded, cross-section view of the wallcovering inaccordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Turning to FIGS. 1 and 2, a polypropylene laminate wallcovering 10comprises a scrim backing layer 12, a specially formulated, orientedpolypropylene (OPP) film forming a substrate layer 14, and a top layer16 comprising either a UV cured, clear coating or a clear orientedpolypropylene film.

The backing layer 12 of the laminate wallcovering 10 is a ‘scrim” orwoven fabric. The backing layer 12 is conventional scrim fabric commonlyused for wallcovering backing and is generally a 100% polyester,although polyester/cotton blends are commonly used as a backing forwallcoverings as well. Based on testing, the scrim construction thatprovided the best performance and finished weight was a scrim having 68ends×38 picks. Lighter weight woven scrims can be utilized, depending onthe finished weight that is required for the laminate wallcovering 10. Arange of woven scrim constructions and fiber combinations were tested inorder to maximize the performance and weight of the finished laminatewallcovering 10. Much of the tensile and tear performance of thelaminate wallcovering 10 is predicated on the woven backing layer 12, orscrim. Table 1 shows the range of wallcoverings tested. Ultimately, the68×38 polyester scrim provided the best balance of weight, flexibility,performance, and cost, although the other scrims shown in Table 1performed satisfactorily.

TABLE 1 Materials Tested: A 1.00 mil WHITE OPP (substrate layer 14) B2.20 mil WHITE OPP (substrate layer 14) C 4.25 mil WHITE OPP (substratelayer 14) D 8.00 mil WHITE OPP (substrate layer 14) E 12.00 mil WHITEOPP (substrate layer 14) F(UV) 0.35 mil CLEAR PROTECTIVE UV COATING (toplayer 16) G(UV) 0.50 mil CLEAR PROTECTIVE UV COATING (top layer 16)H(UV) 0.60 mil CLEAR PROTECTIVE UV COATING (top layer 16) I(UV) 1.30 milCLEAR PROTECTIVE UV COATING (top layer 16) F(OPP) 0.75 mil CLEARPROTECTIVE OPP (top layer 16) G(OPP) 2.20 mil CLEAR PROTECTIVE OPP (toplayer 16) H(OPP) 4.25 mil CLEAR PROTECTIVE OPP (top layer 16) I(OPP)7.00 mil CLEAR PROTECTIVE OPP (top layer 16) K 68 × 38 Polyester Scrim(backing layer 12) L 39 × 26 Polyester Scrim (backing layer 12) M 54 ×42 Polyester/Cotton Scrim (backing layer 12) Combinations Tested: TOPLAYER 16 SUBSTRATE (UV COATING or OPP LAYER 14 FILM) BACKING LAYER 12White OPP Layer Clear Protective Layer Woven Scrim Layer A F(UV) orF(OPP) K-L-M A G(UV) or G(OPP) K-L-M A H(UV) or H(OPP) K-L-M A I(UV) orI(OPP) K-L-M B F(UV) or F(OPP) K-L-M B G(UV) or G(OPP) K-L-M B H(UV) orH(OPP) K-L-M B I(UV) or I(OPP) K-L-M C F(UV) or F(OPP) K-L-M C G(UV) orG(OPP) K-L-M C H(UV) or H(OPP) K-L-M C I(UV) or I(OPP) K-L-M D F(UV) orF(OPP) K-L-M D G(UV) or G(OPP) K-L-M D H(UV) or H(OPP) K-L-M D I(UV) orI(OPP) K-L-M E F(UV) or F(OPP) K-L-M E G(UV) or G(OPP) K-L-M E H(UV) orH(OPP) K-L-M E I(UV) or I(OPP) K-L-M

The substrate layer 14 of the laminate wallcovering 10 is a whiteoriented polypropylene film, ranging in thickness from 1.00 mil to 12.00mil with a preferred thickness of 8.00 mil. Oriented polypropylene filminherently repels foreign matter, like dirt and stains. This repellencycharacteristic of oriented polypropylene film normally includes printinginks. The oriented polypropylene film of the present invention isspecially formulated to bond permanently with a variety of printingmedia (inks) 18 and the adhesives used for lamination. Both the face andback surfaces of the oriented polypropylene film forming substrate layer14 are given a functional treatment to specifically capture and hold inkand adhesive. The process used to enhance the bonding property of theoriented polypropylene film of substrate layer 14 involves both anoxidative treatment and a surface primer applied to the film after theextrusion stage. This process alters the dyne level of the surface ofthe oriented polypropylene film, allowing inks and adhesive to bondpermanently to the treated oriented polypropylene film. The orientedpolypropylene film used in connection with the present invention as thesubstrate layer 14 also has excellent grain capture when embossed.

In connection with the present invention, substrate layers 14 having thefollowing thicknesses were tested: 1.0 mil, 2.20 mil, 4.25 mil, 8.00 miland 12.00 mil thickness. (See Table 1.) The lesser thicknesses of theoriented polypropylene films for the substrate layer 14 exhibitedsomewhat reduced “hiding” properties when installed and somewhat reducedresistance to impact. The higher thicknesses (12.00 mil) of the orientedpolypropylene film exhibited increased stiffness requiring thewallcovering installer to “fight” the wallcovering to get it on thewall. The 8.00 mil thick oriented polypropylene film provided goodperformance while maintaining an acceptable hand, enabling the paperhanger to install the wallcovering with ease. The thicknesses for theoriented polypropylene film for the substrate layer 14 shown in Table 1,however, are all considered within the scope of the invention. Thesource for the oriented polypropylene film used for the substrate layer14 is Applied Extrusion Technologies, Inc. (AET), located at 115 Read'sWay, New Castle, Del. 19720. AET is the only independent global supplierdedicated solely to the manufacturing of oriented polypropylene films,and it currently provides 25% of North America's oriented polypropylenefilm needs. The specific AET 8.00 mil film is sold by AET under theproduct designation 8SPM.

The top layer 16 of the wallcovering 10 is a 0.35 mil to 1.30 mil ultraviolet (UV) cured clear coating with a matte or gloss outer finish. ThisUV clear coating has been formulated by Environmental Inks & Coatings,31 Quality Products Road, Morganton, N.C. 28655 and sold under theproduct designations Matte UF 170689, UV 175 Matte OPV and Gloss UF170690, UV 80gloss OPV. This UV clear coating has been formulated toprovide chemical and abrasion resistance that exceeds standard Type IIPVC wallcovering finishes currently being offered in the market. Thiscoating also provides dry erase properties.

A range of coating weights for the UV cured top layer 16 were tested ondifferent weights of the oriented polypropylene film substrate layer 14as noted in Table 1. The same qualifications (performance, hand, andcost) were used to determine that the UV coating at the 0.35 milthickness, applied with a 200 anilox cylinder provided a good balance ofperformance, hand, and value. Suitable performance, however, wasachieved with coating weights from 0.35 mil to 1.30 mil.

In an alternative embodiment, the top layer 16 of the wallcovering 10 isa 0.75 mil-7.00 mil clear oriented polypropylene film with a matte outerfinish. The oriented polypropylene film used for the top layer 16protects the finished laminate wallcovering 10. The orientedpolypropylene film for the top layer 16 is supplied by AET under thedesignation RLS Mat XZ811. The back side of the clear orientedpolypropylene film top layer 16, facing the substrate layer 14, has beengiven an oxidative treatment to enhance the oriented polypropylenefilm's acceptance of adhesives used for laminating purposes. The face(matte) side of the oriented polypropylene film has been treated with ablend of polymers that create a release property.

A range of weights for the oriented polypropylene film top layer 16 weretested on different weights of the oriented polypropylene film substratelayer 14 as noted in Table 1. The same qualifications (performance,hand, and cost) were used to determine that the 0.75 mil orientedpolypropylene film provided a good balance of performance, hand, andvalue although the other thicknesses, 0.075 mil to 7.00 mil, providedadequate performance.

In order to construct the polypropylene laminate wallcovering 10, theoriented polypropylene film substrate layer 14 is first printed on itsouter surface with the desired ink pattern 18. Where the orientedpolypropylene film is used for the top layer 16 instead of the UV clearcoating, the desired pattern can be printed on the inner surface of theclear, oriented polypropylene film top layer 16. Better printingresults, however, were achieved by printing the oriented polypropylenefilm substrate layer 14 as compared to printing of the orientedpolypropylene film top layer 16. The oriented polypropylene filmsubstrate layer 14 can be printed on existing gravure printing equipmentusing standard water based ink systems, or digitally printed using UVcured ink systems, and laminate wallcovering 10 can be embossed onequipment like that currently used for standard PVC wallcoveringproduction.

Once the polypropylene film substrate layer 14 has been printed, the UVcured clear coating is applied over the printed oriented polypropylenefilm substrate layer 14. The scrim layer 12 is then laminated by meansof heat and/or adhesive to the oriented polypropylene film substratelayer 14. After the layers been laminated, the entire laminatewallcovering 10, now consisting of a) the woven scrim backing layer 12,b) the printed polypropylene film substrate layer 14, and c) the UVcured clear coating top layer 16, is run through an embossing rollerimparting the pattern of choice to the top surface of the laminatewallcovering 10. Because polypropylene has a relatively low melttemperature, a balance of heat and pressure is required in the embossingprocess to maximize the grain capture. Although not considered criticalto the present invention, the good embossing results were achievedwithin the following ranges of temperature, speed, and pressure:

Web temperature: 240 F.-250 F. Line Speed: 35-40 yds/minute Pressure:2800-3100 PSI

With the alternative embodiment using the clear oriented polypropylenefilm for the top layer 16, the clear oriented polypropylene film toplayer 16 is wet laminated to the printed polypropylene film substratelayer 14. The scrim layer 12 is then laminated by means of heat and/oradhesive to the oriented polypropylene film substrate layer 14. Afterthe layers been laminated, the entire laminate wallcovering 10, nowconsisting of a) the woven scrim backing layer 12, b) the printedpolypropylene film substrate layer 14, and c) the clear orientedpolypropylene film top layer 16, is run through an embossing rollerimparting the pattern of choice to the top surface of the laminatewallcovering 10.

With either embodiment of top layer 16, the finished laminatewallcovering 10 has the appearance and hand of standard Type II PVCwallcovering, and can be produced at a lower cost than the PVCwallcovering. The performance properties of the polypropylene laminatewallcovering 10 exceed those of the PVC based product, in particular theabrasion and stain resistance properties. A substantial advantage of thepolypropylene laminate wallcovering 10 is the energy and labor savingscompared to that required for production of conventional PVCwallcoverings.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principals and applications of thepresent invention. Accordingly, while the invention has been describedwith reference to the structures and processes disclosed, it is notconfined to the details set forth, but is intended to cover suchmodifications or changes as may fall within the scope of the followingclaims.

1. A laminate wallcovering comprising: a. a scrim backing layer: b. aprintable, oriented polypropylene film substrate layer; and c. aultraviolet cured clear coating as the top layer.
 2. The laminatewallcovering of claim 1, wherein the ultraviolet cured clear coating hasa thickness is 0.35 mil or greater.
 3. The laminate wallcovering ofclaim 1, wherein the ultraviolet cured clear coating has a thicknessbetween 0.35 mil and 1.30 mil.
 4. The laminate wallcovering of claim 1,wherein the printable, oriented polypropylene film substrate layer hassurfaces oxidized and coated with a primer.
 5. The laminate wallcoveringof claim 1, wherein the printable, oriented polypropylene film substratelayer has a thickness between 1 mil and 12 mil.
 6. The laminatewallcovering of claim 5, wherein the printable, oriented polypropylenefilm substrate layer has a thickness 8.00 mil.
 7. A laminatewallcovering comprising: a. a scrim backing layer: b. a printable,oriented polypropylene film substrate layer; and c. an orientedpolypropylene film top layer.
 8. The laminate wallcovering of claim 7,wherein the oriented polypropylene film top layer has a thickness is0.75 mil or greater.
 9. The laminate wallcovering of claim 7, whereinoriented polypropylene film top layer has a thickness between 0.75 miland 7.00 mil.
 10. The laminate wallcovering of claim 7, wherein theprintable, oriented polypropylene film substrate layer has surfacesoxidized and coated with a primer.
 11. The laminate wallcovering ofclaim 7, wherein the printable, oriented polypropylene film substratelayer has a thickness between 1 mil and 12 mil.
 12. The laminatewallcovering of claim 11, wherein the printable, oriented polypropylenefilm substrate layer has a thickness of 8.00 mil.